Through-the-roof flue and air intake assembly



March 1969 G.L..HERSHEY ETAL 3,430,549

THROUGH-THE-ROOF FLUE AND AIR INTAKE ASSEMBLY Filed Oct. 13. 1966 UnitedStates Patent 2 Claims ABSTRACT OF THE DISCLOSURE A through-the-roofflue and air intake assembly for sealed combustion heaters havingconcentric air intake and flue exhaust pipes, the flue pipe terminatingabove the air intake pipe and both pipes being provided withoutwardly-extending caps. The improvement comprises providing anoutwardly-exposed section of the flue pipe between the caps where theexposed section has a vertical height of from .5 to 2, or preferably .6to .9, times its outside diameter. The upper portion of the flue pipewhich provides the exposed section can have a larger internal diameterthan the portion below the lower cap, the upper portion of the flue pipepreferably providing from 25 to 75% more cross-sectional area than thelower portion thereof.

This invention relates to a through-the-roof flue and air intakeassembly. Devices like the assembly of the present invention aresometimes referred to as roof jacks. They are particularly adapted foruse with sealed combustion heaters. The roof jack of this invention maybe advantageously employed with the sealed combustion wall heaterdescribed in co-pending application Ser. No. 576,884, filed Sept. 2,1966, now Patent No. 3,361,125, entitled Sealed Combustion Wall Heater.

Roof jacks for sealed combustion heaters are known devices which havebeen widely employed in the United States. Representative devices ofthis kind are described in Patents 2,634,720; 2,818,060; 2,754,816; and2,942,600. The roof jack of the present invention is designed as animprovement on such prior art constructions.

In the designing of roof jacks for sealed combustion heaters, it hasbeen recognized that the fresh air intake and the flue gas exhaustshould be located in substantially the same pressure zone. This has ledto the construction of the roof jacks with the fresh air inlet and theflue gas outlet as close together as possible. In the development of thepresent invention, it was discovered that a wider vertical spacingbetween the intake and exhaust positions provides certain importantadvantages. These advantages relate particularly to the minimizing ofwind effects. With prior constructions under some wind conditions, apositive pressure can be developed in the area between the exhaust andintake caps, and this can reduce or even reverse the desired flows offlue gas and combustion air. While it is desired to maintain a lowerpressure adjacent the flue gas exhaust than adjacent the fresh airintake, it is not necessarily desirable to discharge the flue gases atmaximum velocity. Since the rising flue gases strike the inside of thecap covering the top of the flue pipe, the higher the velocity, thegreater the back pressure developed by the reversal of flow direction indischarging the flue gases through the open bottom of the cap.

It is therefore a general object of the present invention to provide animproved through-the-roof vent and air intake assembly whichsubstantially overcomes the problems and difliculties described above.More specifically, it is an object to provide a roof jack of thecharacter 3,430,549 Patented Mar. 4, 1969 described which minimizes windvelocity effects adjacent the flue gas exhaust, and which substantiallyprecludes development of a higher pressure in this area than thepressure adjacent the combustion air intake, although both the exhaustand intake are in substantially the same pressure zone. A related objectis to provide means for reducing the back pressure caused by reversal offlow of the flue gases adjacent the top of the flue pipe. Furtherobjects, advantages, and results will be indicated in the followingspecificaiton.

This invention is shown in an illustrative embodiment in theaccompanying drawing, in which- FIGURE 1 is a side elevational view of athrough-theroof flue and air intake assembly embodying the features ofthe present invention;

FIG. 2 is a side elevational sectional view showing the internalconstruction of the assembly of FIG. 1; and

FIG. 3 is a top view of the assembly with portions broken away to showthe means for attaching or supporting certain of the components.

The roof jack or flue and air intake assembly, as illustrated in FIGS.1-3, may be fabricated primarily from sheet metal, such as aluminum orgalvanized steel. It consists essentially of a series of concentrictubes or sleeves, which are formed or arranged in a particular manner,and which provide combustion air intake and flue gas exhaust passages,and also includes annular flue exhausts and air intake ports which arecovered by suitable caps. The roof jack is adapted for installation onthe roof of a dwelling unit, such as a mobile home, where the roomimmediately below the roof jack is being heated by a wall-type furnacehaving a sealed combustion construction. A furnace of this type isdescribed in co-pending application Ser. No. 576,884, filed Sept. 2,1966, entitled Sealed Combustion Wall Heater.

Turning now to a detailed description of the invention, and lookingfirst at FIG. 1, the assembly can be seen to include an upper or firstcap 10 which is mounted by brackets 11 on a tubular member 12, and alower or second cap 13 which is mounted on a tubular member 14 bybrackets 15. The assembly also includes a horizontallyextending plate16, which is adapted for mounting on the top of the roof, and a shieldor spacer sleeve 17 which is adapted to extend below plate 16 within theroof. The inventive features are more particularly illustrated in FIG.2, which will now be discussed in detail.

Starting from the innermost of the tubular members, the assemblyincludes vertically-extending flue pipe means designated generally bythe number 18. In the illustration given, the flue pipe means is formedfrom tube 19 and the upper portion 20 of tube 21, and it has its lowerportion concentrically enclosing tube 19. The upper tubular portion 20which forms an extension of flue tube 19 is enclosed on the outside bythe tube or sleeve 12 so that tube 12 in effect provides a cylindricalouter surface for the upper portion of the flue pipe means 18. Asindicated in FIG. 2 and shown more clearly in FIG. 3, the upper end oftube 20 provides tabs 21 which are folded downwardly over the upper endof tube 12 to hold it in place. The lower end of tube 12 is providedwith a rolled edge 12a. The upper end of the flue pipe means 18, asprovided by the composite of tube section 20 and tube 12, is open forthe discharge of flue gas as indicated at 22.

As indicated in FIG. 1 and shown more clearly in FIG. 2, the first orupper cap 10 is of concavo-convex configuration and is arranged toextend horizontally over the open upper end 22 of the flue pipe means18, the underside of the cap providing the concave surface against whichthe flue gases are discharged from the top of the flue pipe. Cap 10 issupported in upwardly-spaced relation to opening 22 and the upper end offlue pipe means 18 so that flue gases can exit between the upper end ofpipe means 18 and the inside of cap 10, the desired exit flow beingindicated by the arrows in FIG. 2. Preferably, the lower edge a of cap10 is positioned at a level substantially the same as the upper end ofthe flue means 18. In the illustration given, edge 10a extends slightlybelow the upper ends of tube 12 and tube section 20. The lower portionof cap 10 has a diameter appreciably greater than the outside of sleeve12 to provide a relatively wide annular space 23 for the discharge ofthe flue gases.

Cap 10 may be supported in any suitable manner. In the illustrationgiven, four of the support brackets 11 are provided at 90 spacingsaround tube 12, The triangular shaped brackets 11 include an inner rightangle flange 11a, as shown in FIGS. 1 and 3, which may be spot welded tothe outside of tube 12, and also an outer right angle flange 111), asshown in FIG. 3, which may be spot welded to the inside of the lowerportion of cap 10, thereby firmly supporting cap 10 on tube 12.

The assembly also includes air intake pipe means designated generally bythe number 24. Air intake pipe means 24 is of larger diameter than fluepipe means 18 and is arranged to concentrically enclose the lowerportion of the flue pipe means, extending around tube 19 for most of itslength. In the illustration given, pipe means 24 is formed from a lowertube section 25 and an upper tube section 14. The upper end of pipemeans 24 as provided by tube section 14 terminates at a distance belowthe top of flue pipe means 18, and provides an annular opening 26 forthe intake of air.

Air intake opening 26 is covered by the second or lower cap 13, as shownmore clearly in FIG. 2. Cap 13 is also of concavo-convex configuration,the inner convex surf-ace facing downwardly towards opening 26, and thecap eX- tending horizontally outwardly beyond the sides of tube 14 toprovide an annular intake opening 27. Cap 13 has a central opening 28which receives the adjacent portion of the flue pipe means 18 comprisingthe tube section 20 of tube 21. Cap 10 is supported in upwardly spacedrelation with respect to the top of air intake pipe means 24 and opening26. This permits the air to enter as indicated by the arrow in FIG. 2.

Cap 13 is supported by brackets 15 which are similar in construction andarrangement to brackets 11 which support cap 10. Brackets 15 include aninner right angle flange portion 15a which is spot welded to tube 14 andan outer right angle flange portion 15b which is spot welded to theinside of the lower portion of cap 13, as shown more clearly in FIG. 3.Thus, cap 13 is securely supported on tube 14.

Preferably, as shown, caps 10 and 13 are of substantially identical sizeand configuration. It is particularly desirable that their lowerportions have substantially the same diameter. However, in certainembodiments of the present invention, caps 10 and 13 may be of differentsizes, such as constructions wherein cap 13 has a greater diameter thancap 10.

The roof jack of the present invention is particularly characterized bythe relation of the distances y and x as indicated by the dimensionlines in FIG. 2. The dimension x is the vertical distance between thelower edge 10a of cap 10 and the top or uppermost surface portion of cap13, which is the portion of the cap immediately adjacent the centralopening 28. It will be understood, of course, that the upper surface ofcap 13 curves downwardly from the central portion around opening 28. Thedistance y represents the external diameter (O.D.) of the upper endportion of flue pipe means 18 which extends between the caps 10 and 13.In the illustration given, the outer surface of the flue pipe means atthis point is provided by the outside of tube 12, and therefore thedistance y is the CD. of tube 12. In accordance with the presentinvention, the vertical distance x should equal from .5 to 2 times thediameter y. In preferred embodiments, the distance x equals from .6 t9.9 times the diameter y. For

example, the CD. of tube 12 may be approximately 3.2 inches while thevertical distance x is approximately 2.5 inches. With these specificdimensions, the caps 10 and 13 may have lower portion diameters of about6.75 inches. The overall height of the assembly from plate 14 to the topof cap 10 can be about 9 inches, while the clearance between the loweredge of cap 13 and plate 14 can be about 3 inches.

Also, in accordance with the present invention, the upper portion offlue pipe means 18 may have a larger internal diameter than the lowerportion. For example, tube 19 has a substantially smaller internaldiameter than tube section 21 which forms the upper portion of the fluemeans. The transition between the diameter of pipe 19 and the diameterof pipe section 20 is provided by the enlarged connecting portion 19a,which can be united to tube 21 immediately below its section 20 by spotor arc welding. Preferably, the connection at this point providessubstantially a hermetic seal so that the annular space 29 between tubes19 and 21 is essentially a dead air space with no communication with theflue outlet.

In the preferred embodiment, as shown, the enlarged upper portion of theflue pipe means 18 begins at about the top of cap 13 and extendsthereabove to the flue outlet 22. However, the principal requirement isthat the upper portion of the flue pipe means has an increased internaldiameter as compared with the lower portion. The upper portion of theflue pipe therefore provides a greater cross sectional area as comparedwith the lower portion, thereby reducing the velocity of the flue gasesbefore they impinge on the underside of cap 10.

In a specific preferred embodiment, the internal diameter of tube 19 canbe approximately 2.5 inches, while the internal diameter of tube section20 is approximately 3.1 inches. With this construction, the upperportion of the flue outlet provides about 50% greater cross sectionalarea than the lower portion. In other embodiments, the cross sectionalarea of tube section 20 may be from 25 to greater than the crosssectional area of tube section 19.

The lower portion of tube 20 which surrounds tube 19 and is separatedtherefrom by the annular space 29 serves as a jacket for the flue. Thisjacketing arrangement minimizes the transfer of heat from the flue gasto the incoming hot air by supplying cooler air to the furnace, whichimproves combustion capacity.

The lower ends of tubes 20 and 18 may be flared to facilitate theinsertion of connecting pipes. In the inwardly formed rib 19b toward theupper portion of tube 19 serves as a stop for the upper end of the fluepipe. It will be understood that connecting pipes will also be insertedwithin tube 29 and around the outside of tube 25, thereby providingcontinuous flow passages. No tubular member will usually be connectedwith shield 17, since this is not designed to provide a flow passage.When the unit is installed, the plate 14 will be at the roof level, andthe portions of the assembly above plate 14 will extend above the roofline.

The operation of the roof jack will be largely apparent from theforegoing description. However, the salient features may be brieflysummarized as follows. The flue gases rise through the tube 19 and thenexpand outwardly into the increased volume of the tube section 20, whichhas the result of reducing the velocity of the flue gases. The fluegases of reduced velocity are directed against the inside of cap 10 andare caused to reverse their flow, being discharged through the annularoutlet 23. The pressure maintained adjacent the outlet 23 will be lowerthan the pressure adjacent the fresh air inlet 27. This will be trueeven under adverse wind conditions due to the spacing provided betweenthe caps 10 and 13, as described above.

While in the foregoing specification this invention has been describedin relation to a specific embodiment thereof and many details have beenset forth for purposes of illustration, it will be apparent to thoseskilled in the art the invention is susceptible to other embodiments,and that certain of the details described herein can be varied withoutdeparting from the basic principles of the invention.

We claim:

1. A through-the-roof flue and air intake assembly for a sealedcombustion heater, including vertically-extending flue pipe means havingan upper portion with a cylindrical outer surface and an open upper end;a first horizontally-extending concavo-convex cap supported over saidflue pipe means upper end, said cap terminating at a lower end having adiameter greater than said flue pipe means and said cap means beingsupported in spaced relation to said flue pipe means upper end so thatflue gases can exit between said upper end and the inside of said cap;air intake pipe means of larger diameter than said flue pipeconcentrically enclosing the lower portion thereof, said air intake pipehaving an open top terminating at a distance below the top of said fluepipe means; and a second horizontally-extending concave-convex capproviding a central opening receiving said flue pipe, said second capbeing of larger diameter than said air intake pipe means and beingsupported in spaced relation to said air intake pipe means top so thatair can enter between the inside of said second cap and the outside ofsaid air intake pipe means top: wherein the improvement comprises havingthe cylindrical outer surface of the portion of said flue pipe betweensaid first and second caps directly exposed to the outside atmospherewhile being dimensioned to control wind effects, said exposed flue pipeportion between said first cap lower edge and the upper surface of theportion of said second cap around said opening having a vertical lengthequalling from .6 to .9 times its outside diameter, said exposed fluepipe portion internally providing a substantially sealed extension ofsaid flue pipe with a larger internal diameter than the portion thereofbelow said second cap, the said enlarged upper portion of said flue pipehaving from 25 to 75% more cross-sectional area than the said smallerlower portion thereof.

2. A through-the-roof flue and air intake assembly for a sealedcombustion heater, including vertically-extending flue pipe means havingan upper portion with a cylindrical outer surface and an open upper end;a first horizontally-extending cap supported over said flue pipe meansupper end, said cap terminating at a lower end having a diameter greaterthan said flue pipe means and said cap means being supported in spacedrelation to said flue pipe means upper end so that flue gases can exitbetween said upper end and the inside of said cap; air intake pipe meansof larger diameter than said flue pipe concentrically enclosing thelower portion thereof, said air intake pipe means having an open topterminating at a distance below the top of said flue pipe means; and asecond horizontally-extending cap providing a central opening receivingsaid flue pipe means, said second cap being of larger diameter than saidair intake pipe means and being supported in spaced relation to said airintake pipe means top so that air can enter between the inside of saidsecond cap and the outside of said air intake pipelmeans top; theimprovement characterized by the cylindrical outer surface of theportion of said flue pipe between said first and second caps directlyexposed to the outside atmosphere while being dimensioned to controlwind effects, said exposed flue pipe portion between said first caplower edge and the upper surface of the portion of said second caparound said opening having a vertical length equalling from .5 to 2times its outside diameter, and the portion of said flue pipe above saidsecond cap providing a substantially sealed extension of said flue pipewith a larger internal diameter than the portion of said flue pipe belowsaid second cap, the said enlarged upper portion of said flue pipehaving cross-sectional area of from 25% to greater than the said smallerlower portion thereof.

References Cited UNITED STATES PATENTS 855,607 6/1907 Baggaley 98622,634,720 4/1953 Thulman 126307 2,754,816 7/ 1956 Ryder 98-46 XR2,755,794 7/1956 Wendell 98-32 XR 3,105,432 10/1963 Chamberlain 98--48XR 3,304,930 2/1967 Cayot 126--85 3,315,586 4/1967 Marapese 126307 XR3,094,980 6/1963 Inabnit 98-46 XR FOREIGN PATENTS 502,899 12/ 1954Italy.

FRED C. MATTERN, JR., Primary Examiner. MANUEL ANTONAKAS, AssistantExaminer.

